Particle supply valve for use in blasting apparatus

ABSTRACT

A blasting apparatus has two or more pressured tanks and a switching member for selecting one of the pressured tanks from which particles are to be fed to an ejection portion, thereby which enabling a continuous blasting operation. The blasting apparatus has a particle supply valve which uses a valve rod and piston arrangement for preventing leakage of particles. Such a valve arrangement enables airtightness to be retained within pressurized chambers of the valve housing for a long period of time.

This is a Divisional of application Ser. No. 08/564,290 filed Dec. 21,1995, now U.S. Pat. No. 5,800,246, which is a national stage ofPCT/JP95/00800 filed on Apr. 24, 1995.

FIELD OF THE INVENTION

The present invention relates to a blasting apparatus, and in particularrelates to a pressured tank apparatus for supplying abrasive particlesin a nozzle of a blasting apparatus. Further, the present invention isalso directed to a method of switching the pressured tank apparatus, aparticle supply valve which opens or closes to respectively create orterminate a flow of particles and compressed air to a nozzle of ablasting apparatus, and a particle separator that extracts onlyreclaimable particles from a mixture of used particles and dust whichhave been produced during the blasting process.

BACKGROUND ART

In the conventional blasting apparatuses, a pressured tank apparatusthat supplies abrasive particles to a nozzle is constructed from apressured tank as shown in FIG. 6, which is so called as a singledirect-pressure type. In the drawing, the reference numeral 51 denotessuch a pressured tank. On the pressured tank 51, there is provided ahopper 52. Between the pressured tank 51 and the hopper 52, there isprovided a particle supply valve 56. The particle supply valve 56 is apressure type shutoff valve which opens and closes automatically inaccordance with the internal pressure of the pressured tank 51.

Further, connected to the top portion of the pressured tank 51 are anair supply pipe 55, which supplies air for the purpose of pressurizingthe inside of the pressured tank 51, and an exhaust pipe 58 whichexhausts the pressurized air within the pressured tank 51. Forperforming these functions, the air supply pipe 55 is provided with anair supply valve 54, and the exhaust pipe 58 is provided with an airrelease valve 57.

Connected to the bottom portion of the pressured tank 51 is a deliverypipe 60 for delivering compressed air and particles to a nozzle (notshown in FIG. 6). A particle supply valve 59 is provided in the deliverypipe 60. In the drawing, the reference numeral 53 denotes particlesaccumulated within the pressured tank 51.

Now, when the above described conventional blasting apparatus is to beused, first a prescribed amount of particles are supplied to thepressured tank 51 from the hopper 52. Then the exhaust valve 57 isclosed and the air supply valve 55 is opened to allow pressurized air topass into the pressured tank 51, whereby the pressure inside thepressured tank 51 is to be risen. As soon as the pressure inside thepressured tank 51 reaches a prescribed level, the particle supply valve56 automatically closes, thus stopping the flow of particles 53 from thehopper 52 to the pressured tank 51 and, at the same time, preventingpressurized air from leaking into the hopper 52 from the pressured tank51. Then when a blasting operation is to be carried out, the particlesupply valve 59 is opened to allow particles to be delivered to thenozzle.

However, in the conventional blasting apparatuses, when all theparticles 53 have been used up in the course of carrying out a blastingoperation, the blasting operation must be suspended temporarily in orderto refill the pressured tank 51 with the new particles 53. Namely, inthe refilling operation, the air supply valve 54 must first be closed tostop the flow of pressurized air into the pressured tank 41 after theblasting operation has been suspended. At the same time, the exhaustvalve 57 must be opened to exhaust pressurized air out of the pressuredtank 51. Then, when the pressure inside the pressured tank 51 reaches apressure that is roughly equal to the atmospheric pressure, the particlesupply valve 56 automatically opens, which then allows particles 53 toflow into the pressured tank 51 from the hopper 52. Consequently, in theconventional blasting apparatuses, a great deal of time and many tediousoperations are required for refilling the pressured tank 51, andtherefore blasting operation must be suspended at each refillingoperation. For this reason, there is a problem in that it is impossibleto carry out a continuous blasting operation with such conventionalblasting apparatuses.

In order to reduce the number of such suspensions which are caused bythe refilling operations as much as possible, one attempt has been madeto utilize a larger pressured tank that can accommodate a great deal ofparticles therein. In this way, it is possible to carry out a relativelylonger blasting operation with one operation of particles.

However, even with the blasting apparatuses having such larger pressuredtanks, it is still necessary to suspend blasting operations in order torefill the pressured tank, and therefore it is impossible to carry outcontinuous blasting operation. Further, such a larger pressured tank ismore dangerous in comparison with a small pressured tank, and amanufacturing cost thereof is relatively high. Furthermore, there is aproblem in that a place where such a blasting apparatus having a largerpressured tank is to be installed must be limited in view of its weightand a large amount of space which is required to install such a blastingapparatus.

In view of the problems in the conventional apparatuses described above,it is a first object of the present invention to provide a compact sizepressured tank apparatus for use in a blasting apparatus which enables acontinuous blasting operation to be carried out, as well as a method ofswitching the pressured tank apparatus. Namely, in the blastingapparatus, a plurality of small pressure tanks are employed, and apressured tank from which particles are provided to a nozzle is selectedfrom the plurality of pressured tanks and at the same time particles aresupplied or refilled to another pressured tank which is not providingparticles to the nozzle.

In the meantime, in the conventional blasting apparatuses, a particlesupply valve is provided for performing or terminating the supply ofparticles which are to be fed to the nozzle.

As one example of such conventional particle supply valves, there isknown a valve of the type as shown in FIG. 9.

The known valve has a valve housing 221 provided with an inlet port 222into which particles flow, an outlet port 223 from which the particlesflow out of the valve, and a control air inlet/outlet port 224 whichallows control air to flow into or out of the valve.

Further, in the valve housing 221, there are provided two diaphrams 229,230 which are made of flexible rubber and held by the valve housing 221to partition the space inside the valve housing 221 into a first chamber231 and a second chamber 232. In this construction, the inlet port 222and the outlet port 223 are communicated with the first chamber 231, andthe control air inlet/outlet port 224 is communicated with the secondchamber 232.

Further, a metal pin 227 is passed through the middle portion of each ofthe two diaphrams 229, 230 and is fixed thereto. Fixed to the end of themetal pin 227 which lies in the first chamber 231 is a valve element226, and fixed to the other end which lies in the second chamber 232 isa metal plate cap 228.

Now, when the valve is to stop supplying the nozzle (not shown in FIG.9) with particles , control air is passed into the second chamber 232through the control air inlet/outlet port 224 to pressurize the secondchamber 232. This results in an increase in pressure inside the secondchamber 232 which causes the flexible diaphram 230 to deform toward thefirst chamber 231, which in turn causes the valve element 226 to closeoff the valve seat 225, thereby closing off the inlet port 222.

Then, when the valve is to be opened to supply the nozzle with particles, control air is exhausted out of the second chamber 232 through thecontrol air inlet/outlet port 224 in order to decrease the pressureinside the second chamber 232. As a result, the diaphram deforms towardthe second chamber 232, thus causing the valve element 226 to beretracted from the shutoff position (i.e., it moves to the right side inFIG. 9). This then allows particles to flow into the first chamber 231through the space between the valve seat 225 and the valve element 226.Thereafter, the particles flow out of the outlet port 223 and thensupplied to the nozzle.

Further, the second chamber 232 is provided with an adjusting screw 233and a handle 234 fixed to the screw 233 to allow the screw 233 to berotated. The screw 233 is used to adjust the amount of retraction of thevalve element 226 in order to adjust the amount of particles to besupplied to the nozzle. For example, when the amount of particlesflowing through the valve is to be decreased, the screw 233 is rotatedto increase its protruding length into the second chamber 232. In thiscase, the end of the metal cap 228 provided at the middle of thediaphram 229 that has been deformed into the second chamber 232 upon thesupply of the particles is come into contact with the end of the screw233, to restrict the retraction of the valve element 226. As a result,the amount of the space between the valve element 226 and the valve seat225 is reduced, thereby achieving a reduction in the amount of supply ofparticles.

However, because the diaphrams 229, 230 of the conventional valves aremade of rubber, they lose elasticity during the long-term use, and thisresults in a problem in that leakage of particles is liable to becaused. Namely, when control air is supplied to the second chamber 232to deform the diaphram 230 toward the first chamber 231, it is notpossible to obtain a required pressing force that pushes the valveelement 226 onto the valve seat 225 if the diaphram 230 loses itselasticity. Consequently, the valve element 226 is pushed back due tothe pressure of the particles, thus leading to the leakage thereof.

Furthermore, because the rubber diaphrams 229, 230 are flexible, it isnot possible to guarantee an even movement of the metal pin 227. Namely,when the supply of particles is terminated, the metal pin 227 isnormally moved to the left in the drawings. However, there is a casethat the pin 227 moves slightly left-downward due to the weight of thevalve element 226. In this case, since the valve element 226 which isfixed to the metal pin 227 does not properly engage with the valve seat225, there is a case that a space is created between the valve element226 and the valve seat 225, thus resulting in a problem in thatparticles and compressed air are leaked through the space.

Moreover, if the power to the blasting apparatus is accidentally shutoff during a blasting operation and therefore the flow of control air tothe second chamber 232 suddenly stops, there is another problem in thatparticles and compressed air are discharged from the outlet port 223.Namely, in the above condition, the valve element 226 is simply abuttedonto the valve seat 225 by the restoring force of the diaphram 229, 230,so that they are easily retracted by the pressure of compressed air andparticles, thus resulting in leakage of the compressed air andparticles.

In view of the above described problems, it is a second object of thepresent invention to provide a leakproof particle supply valve for usein a blasting apparatus which uses a piston and a biasing means in theform of a regulating spring instead of a diaphram to avoid deteriorationof flexibility characteristics.

Further, it is a third objection of the present invention to provide aparticle supply valve equipped with a slide disc fixed to a valve rod toallow a seal to be maintained between a first chamber and a secondchamber over a long period of time.

Furthermore, it is a fourth object of the present invention to provide aparticle supply valve which can prevent leakage of pressurized air andparticles from being caused, by holding the valve rod properly to closethe valve seat at a predetermined position.

Moreover, it is a fifth object of the present invention to preventdischarge of pressurized air and particles which would be caused by anaccident that the valve element is not retracted from the valve seat ina case where flowing and pressurizing of the control air accidentallystop during the blasting operation.

In the meantime, in blasting apparatuses, particle separators have beenused for the purpose of recycling particles that have been used during ablasting process. Namely, in the blasting process, some of the particlesare crushed into particle dust. However, in order to maintain a desiredblasting performance, it is necessary for the particles to maintaintheir prescribed particle diameter. Therefore, it is necessary toprovide a particle separator for removing such particle dust in order toreclaim the particles.

In the conventional apparatuses, a cyclone type particle separator isused as such particle separator. This particle separator separatesreclaimable particles from particle dust and the like by utilizing arevolving air current which produces a centrifugal force. This utilizesthe character that particle dust has a relatively small diameter ratherthan a prescribed particle and therefore the mass of the particle dustis smaller than that of the reclaimable particles.

In this connection, FIG. 14 is a longitudinal sectional side view ofsuch a cyclone type particle separator, and FIG. 15 is a top plane viewthereof.

In FIG. 14 the reference numeral 350 denotes a separating chamber. Inthe separating chamber 350, there is provided with an inlet port 351which sucks a mixture of used particles and particle dust produced by ablasting process together with compressed air. Further, an exhaust port354 is provided in a central portion of the separating chamber 350 insuch a manner that is passes through the upper surface of the separatingchamber 350.

Now, when the mixture of used particles and particle dust produced by ablasting process and compressed air are sucked into the inside of theseparating chamber 350 through the inlet port 351, they form a revolvingflow that valve seat in the direction indicated by the arrow 352 shownin FIG. 15. Then, due to the relatively large mass of each of suchprescribed diameter reclaimable particles and the centrifugal forceproduced by such revolving flow, the reclaimable particles slowly movedown toward the bottom of the separating chamber 350 as they flow in thevicinity of the inner circumferential side walls of the separatingchamber 350. Upon reaching the bottom of the separating chamber 350, thereclaimable particles are collected in a hopper tank 355.

In this case, the unreclaimable particle dust flows more toward thecenter of the separating chamber 350 due to their relatively low mass.Consequently, such low-mass particle dust gets sucked out of theseparating chamber 350 together with compressed air through the exhaustport 354, and then fed to a dust collector.

In FIGS. 14 and 15, a metal screen indicated by the numeral 353 isprovided for preventing peeled coating or bits of paint which have arelatively large size and has been discharged during the blastingprocess with being mixed into the reclaimable particles. This is becausethere is a case that such peeled coating or bits of paint falls into thehopper tank 355 without being discharged from the discharge port.

However, because such conventional particle separators do not have anyobstructive member inside the separating chamber for diffusing themixture of reclaimable particles and particle dust, a mixture of largeand small mass particles and particle dust is caused to flow in thevicinity of the inner circumferential side walls of the separatingchamber 350 when the particle separator is in actual operation, thusrendering such centrifugal separation ineffective. Furthermore, it isnot possible to achieve a sufficient centrifugal separation with suchconventional separators because the mixture of reclaimable particles andparticle dust either falls into the hopper tank 355 or is sucked outthrough the exhaust port 354 before the mixture has flowed even halfwayaround the inside of the separating chamber 350. For these reasons, suchconventional particle separators do not perform an accurate separationof reclaimable particles and particle dust.

Furthermore, if relatively large material such as peeled coating whichhas been exhausted in the blasting process would enter into theseparating chamber, the revolving air flow is disturbed. In theconventional apparatus, the centrifugal force required for theseparation process is obtained by the stable revolving air flow, thereis a problem in that such a disturbance of the revolving air flowdeteriorates stable separation accuracy.

Accordingly, it is a sixth object of the present invention to provide aparticle separating apparatus for use in a blasting apparatus which canachieve a highly accurate separation of particles by using a diffusionmember instead of a centrifugal force, and thereby being able to havehigh accuracy of separation and excellence in stable particle separationaccuracy.

DISCLOSURE OF THE INVENTION

In order to achieve the objects stated above, the pressured tankapparatus according to the present invention comprises two or morepressured tanks, and a switching member for selecting from the two ormore pressured tanks one pressured tank from which particles are to besupplied to a nozzle of the blasting apparatus, wherein one pressuredtank or another pressured tank from which the particles are to besupplied to the nozzle of the blasting apparatus is switched to anotherpressured tank or one pressured tank by operating the switching means;and particle supply valve and air release valve of one or anotherpressured tank are closed while an air supply valve of another or onepressured tank is opened, thereby supplying the particles in theswitched pressured tank to the nozzle.

As described above, in the pressured tank apparatus according to thepresent invention, a pressured tank from which particles are supplied toa nozzle is selected from a plurality of pressured tanks, while theother tank or tanks which are not in use are being refilled withparticles, thus making it possible to carry out a continuous blastingoperation.

Further, the particle supply valve according to the present invention,comprising: a valve housing having an inside space; partition wall fordefining the inside space of the valve housing into a first chamber anda second chamber; a particle inlet port and a particle outlet port bothprovided in the first chamber; a control air inlet/outlet port providedin the second chamber; a valve rod which passes the partition wall in aslidable manner, the valve rod having a first end portion positioned inthe first chamber and a second end portion positioned in the secondchamber; a closure member provided at the first end portion of the valverod; a piston fixedly mounted to the valve rod in the second chamber;and a biasing means in the form of a regulatory spring for pressing thesecond end portion of the valve rod.

According to the particle supply valve having the above describedstructure, since the particle supply valve does not use partition wallmade of rubber, it is possible to avoid the deterioration in elasticityassociated with such construction as used in the conventional valve. Asa result, the present invention provides a particle supply valve whichprevents leaking of particles and pressurized air. Further, according toabove described construction, by supplying or discharging the controlair, it is possible to move the piston with the use of the biasing forceof the regulating spring to slide the valve rod, and thereby enabling toclose or open the valve seat with the valve element precisely at aprescribed position. Further, according to the above construction, inthe event that the power source is erroneously or accidentally shut offduring the blasting operation to terminate that control air flows intothe second chamber and pressurize it, the valve element is not retractedfrom the valve seat because the biasing means pushes the valve rod.Therefore, even in such a case, it is possible to prevent the compressedair and particles from being ejected from the outlet port.

Further, a slide disc may be fixed to the valve rod within the firstchamber. By doing so, it is possible to prevent particles from enteringinto sliding surfaces between the insertion hole and the valve rod, thusmaking it possible to maintain an airtight seal between the firstchamber and the second chamber over a long period of time.

Furthermore, the particle separator for use in the blasting apparatusaccording to the present invention comprises: a separating chamber; anintake port for blowing reclaimable particles and particle dust obtainedafter the blasting operation into the separating chamber; a diffusionmember for diffusing the reclaimable particles and particle dust; anexhaust port for exhausting the particle dust and compressed air; and areclaimable particle accommodating tank disposed below the diffusionmember.

According to the particle separator having the above describedstructure, since the reclaimable particle and particle dust areefficiently diffused by the diffusion member, it is possible to improvethe separation accuracy. Further, since centrifugal force caused byrotating air flow is not used, it is possible to obtain stableseparation accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of one embodiment of a blasting apparatusaccording to the present invention, which shows process for supplyingparticles to first and second pressured tanks;

FIG. 2 is a sectional view of the embodiment of the blasting apparatusaccording to the present invention, which shows the condition in whichparticles are supplied to a nozzle from the first tank to carry out ablasting operation;

FIG. 3 is a sectional view of the embodiment of the blasting apparatusaccording to the present invention, which shows the condition in whichreclaimable particles or the like are fed from a blasting operationchamber to a particle separator by using compressed air;

FIG. 4 is a sectional view of the embodiment of the blasting apparatusaccording to the present invention, which shows the condition that theparticles are supplied to the nozzle from the second tank, whileparticles are supplied to the second tank;

FIG. 5 is a time chart for the pressured tank apparatus of theembodiment shown in FIGS. 1 to 4, and it shows a sequence process in theapparatus;

FIG. 6 is a sectional view of the convention pressured tank apparatus;

FIG. 7 is a cross-sectional view which shows the condition in which aninlet of one embodiment of a particle supply valve according to thepresent invention is closed;

FIG. 8 is a cross-sectional view which shows the condition that theinlet of the particle supply valve shown in FIG. 7 is opened;

FIG. 9 is a cross-sectional view of the conventional particle supplyvalve;

FIG. 10 is a longitudinal sectional side view of a particle separatorfor use in an embodiment of the blasting apparatus according to thepresent invention;

FIG. 11 is a transverse sectional view of the particle separator shownin FIG. 10;

FIG. 12 is a perspective view of a diffusion member of the particleseparator shown in FIG. 10;

FIG. 13 is a perspective view of a diffusion member of anotherembodiment of the particle separator according to the present invention;

FIG. 14 is a side view which shows a particle separator of theconventional cyclone type;

FIG. 15 is a top plan view of the particle separator shown in FIG. 14;and

FIG. 16 is an exploded perspective view of the particle separator shownin FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, a detailed description of the preferredembodiments will now be given below.

FIGS. 1-4 are sectional views of a blasting apparatus equipped with apressured tank apparatus according to the present invention. Theblasting apparatus is comprised of a pressured tank apparatus, ablasting chamber and a particle separator, which are described below inthat order.

The pressured tank apparatus includes two pressured tanks 1, 11 actingas a particle storage means. Each of the first and second pressuredtanks 1, 11 is made from a cylindrically shaped member having upper andlower flanges and top and bottom cover plates which are fastened to theupper and lower flanges with bolts and nuts, respectively. Connected tothe top cover plates of the pressured tanks 1, 11 are air supply pipes2, 12 for supplying pressurized air to the pressured tanks 1, 11,exhaust pipes 4, 14 for discharging pressurized air out of the pressuredtanks 1, 11, and particle supply pipes 6, 16 for supplying particlesfrom a hopper 304 to the pressured tanks 1, 11. Further, air supplyvalves 3, 13 are provided in the air supply pipes 2, 12, air releasevalves 5, 15 are provided in the exhaust pipes 4, 14, and particlesupply valves 7, 17 are provided in the particle supply pipes 6, 16,respectively. Connected to the bottom cover plates of the pressuredtanks 1, 11 are particle discharge pipes 9, 19 for discharging particlesout of the pressured tanks 1, 11, and connected to the particledischarge pipes 9, 19 is a directional control valve 20.

In this arrangement, the air supply valves 3, 13, the air release valves5, 15, the particle supply valves 7, 17 and the directional controlvalve 20 are controlled by a hand-operated switch (not shown in thedrawings) for selecting one of the pressured tanks 1, 11 to whichparticles are to be supplied. In this connection, it is preferred thatthe switching operations of the particle supply valves 7, 17 be carriedout after the switching operations of the air supply valves 3, 13,exhaust valves 5, 15 and directional control valve 20 have beencompleted. To accomplish this, a timer (now shown in the drawings) maybe provided to delay a prescribed length of time the switchingoperations of the particle supply valves 7, 17, when the hand-operatedswitch is operated to carry out the switching operations. Connected tothe directional control valve 20 is a delivery pipe 23 provided with aparticle supply valve 200. This particle supply valve 200 iscooperatively connected to a nozzle switch (not shown in FIGS. 1 to 4).In this regard, it should be understood that the particle supply valve200 may be constructed from a conventional particle supply valve havingpartition walls made of rubber. However, if such is done, there is apossibility that leakage would occur due to the deterioration of theelasticity of the rubber. Furthermore, a pipe indicated by the referencenumeral 22 is a pressured air supply pipe, which is connected to thedelivery pipe 23 to add highly pressurized air to the compressed air andparticles passing through the delivery pipe 23.

The blasting chamber is comprised of an operation chamber 25 and ahopper 26 provided at the bottom of the operation chamber 25. Providedinside the operation chamber 25 for carrying out blasting operations isa nozzle 24 provided at the tip of the delivery pipe 23. At the bottomof the hopper 26, particle ejected from the nozzle 24 are to beaccumulated, which include reclaimable particles, particles of dustwhich are produced from some particles that have been crushed during theblasting operation and peeled coating or flake of paint. Connected tothe bottom of the hopper 26 is a delivery pipe 29 for delivering thesubstances that have accumulated at the bottom of the hopper 26 asdescribed above to the separator 300. In this connection, the deliverypipe 29 is provided with a particle delivery valve 27 which is connectedto the bottom of the hopper 26. Further, a pipe indicated by thereference numeral 28 is a pressurized air supply pipe 28 which isconnected to the particle delivery valve 27 for supplying highlypressurized air to the delivery pipe 29 in order to force reclaimableparticles and particles of dust to the separator 300 through thedelivery pipe 29. Also, provided in the hopper 26 is a level sensor (notshown in the drawings) which sends a signal to a control device (notshown in the drawings) when the amount of used particles, etc.accumulated in the hopper 26 reaches a predetermined volume. In thisconnection, upon receiving a signal from the level sensor, the controldevice is operated so as to open the particle delivery valve 27 tosupply the highly pressurized air through the air supply pipe 28,thereby delivering used particles, etc. to the particle separator 300.

The particle separator 300 is an apparatus for separating reclaimableparticles from particle dust, etc. As shown in FIG. 1, the particleseparator 300 is comprised of a cylindrically shaped outer chamber 302,a cylindrically shaped separating chamber 303 concentrically arrangedwithin the outer chamber 302, and a hopper tank 304 arranged below theseparating chamber 303 to collect reclaimable particles. The deliverypipe 29 is connected to an upper portion of the cylindrical wall of theseparating chamber 303 to allow reclaimable particles, particle dust,etc. produced during a blasting process to be passed together withcompressed air from the delivery pipe 29 into the separating chamber303. Further, a first exhaust opening 307 is provided in a top portionof the separating chamber 303, and five diffusion plates 311a, 311b,311c, 311d and 311e are arranged inside the separating chamber 303. Thediffusion plates 311a, 311b, 311c, 311d and 311e are made of a punchedmetal, respectively and they are mounted on a supporting rod 312 in sucha manner that they are spaced through a predetermined interval. Thediffusion plates 311a-311e have already roughly the same diameter asthat of the separating chamber 303. In this connection, the arrangementof the supporting rod 312 and the diffusion plates 311a-311e isremovable from the outer chamber 302 by opening an outer cover 314provided at the top of the outer chamber 302 and pulling sucharrangement out of the separating chamber 303. Further, a second exhaustopening 308 is formed in the upper part of the hopper tank 304 andparticle supply pipes 6, 16 are connected to the bottom of the hoppertank 304. Connected to the right side of the outer chamber 302 is anexhaust pipe 319 for sucking out particle dust, etc. and sending suchparticle dust to a dust collector (not shown in the drawings).

Furthermore, it is possible to use a commonly known cyclone typeseparator in place of the inventor's proposed particle separatordescribed above. In this regard, it should be noted that because suchcyclone type separators lack a particle diffusion means, and separationof reclaimable particles and dust is carried out only by utilizingcentrifugal force, a mixture of particles and dust are liable to fallinto the hopper. Therefore, the cyclone type separators have relativelypoor separation efficiency in comparison with the inventor's proposedparticle separator.

Hereinbelow, the operation of the blasting apparatus according to thepresent invention will be described with reference to FIGS. 1-4.

First, particles are supplied to the hopper 26 of the blasting chamber.When the volume of particles in the hopper 26 reaches a prescribedlevel, the level sensor sends a signal to the control device. Uponreceiving such signal, the control device opens the particle deliveryvalve 27 and activates a device to supply pressurized air through theair supply pipe 28 to force these particles to be delivered to theparticle separator 300 through the delivery pipe 29. The particles whichare delivered to the particle separator then flow into the separatingchamber 303 where they pass through the holes in the punched metaldiffusion plates 311a-311e and fall into the hopper 34. At this point inthe process, there is no need to activate the dust collector, becausethe particles reaching the particle separator 300 from the hopper tank26 have not yet been used for carrying out a blasting operation, andtherefore not mixed with dust or flake of paint. Now, after falling intothe hopper 34, the particles pass into the particle delivery pipes 6, 16and through the particle supply valves 7, 17, which are both open atthis time, and then fall into the first and second pressured tanks 1, 11at approximately the same amount. While this filling process is beingcarried out, the air release valves 5, 15 are kept open, the air supplyvalves 3, 13 are kept closed, and the particle supply valve 200 is alsokept closed to prevent particles from leaking into the particle deliverypipe 23 (See FIG. 1).

Next, after a prescribed amount of particles have been supplied to thefirst and second pressured tanks 1, 11, the directional control valve 20is switched to the side of the first pressured tank 1 by operating achangeover switch (not shown in the drawing). In this case, it should benoted that in a case where the directional control valve 20 has beenalready switched to the side of the first pressured tank 1, thedirectional control valve 20 is not operable even when the changeoverswitch is operated. At the same time, the operation of the changeoverswitch causes the particle supply valve 7 and the air release valve 5 toclose, and the air supply valve 3 to open to allow compressed air toflow into the second pressured tank 11 in order to pressurize the insideof the first pressured tank 1. At this point, the preparations neededfor carrying out a blasting operation are completed. In this connection,FIG. 5 is a diagram which shows the open/closed states for each valve,wherein the step of preparing a blasting operation is indicated by"Start A".

Now, when a blasting operation is to begin, a nozzle switch (not shownin the drawings) is operated to open the particle supply valve 200 toallow particles and compressed air from the first pressured tank 1 topass through the particle discharge pipe 9 and the particle deliverypipe 23. Upon reaching the end of the particle delivery pipe 23, theparticles are ejected out of the nozzle 24 together with the pressurizedair. In this connection, because the pressurized air that passes out ofthe pressured tank 1 together with the discharged particles may not havesufficient force to create an adequate blasting force from the nozzle24, the compressed air supply pipe 22 is activated to add highlypressurized air (2-5 kg/cm²) to the particles and compressed air passingthrough the particle delivery pipe 23 from the first pressured tank 1(see FIG. 2).

As the blasting operation continue, the amount of particles contained inthe first pressured tank steadily decreases. At the same time, there isa steady piling up of used particles and particle dust, bits of paint,etc. in the hopper 26 of the blasting chamber. Now, when the volume ofused particles and particle dust in the hopper 26 reaches a prescribedlevel, the level sensor sends a signal to the control device. Uponreceiving such signal, the control device opens the particle deliveryvalve 27 and activates a device to supply pressurized air through theair supply pipe 28 to force the reclaimable particles and the like to bedelivered to the particle separator 300 through the delivery pipe 29(see FIG. 3). The beginning of this operation is indicated by "LevelSensor ON (1)" shown in FIG. 5.

As the reclaimable particles, particle dust and bits of paint are beingtransported to the particle separator 300 through the delivery pipe 29,a dust collector (not shown in the drawings) which is connected to theexhaust pipe 319 is activated. Consequently, a negative pressure iscreated in the outer chamber 302, and this causes the usable particlesand particle dust and the like approaching the end of the delivery pipe29 to be suddenly sucked into the separating chamber 303. Thereclaimable particles and particle dust that have entered into theseparating chamber 303 then strike onto the inner walls of theseparating chamber 303 and the top surface (the particle receptionsurface) of the uppermost diffusion plate 311a at high velocity, andthen they become dispersed. At this time, because the particle dust hasa smaller mass than the blasting particles, it gets sucked out of theseparating chamber 303 through the exhaust opening 307. Then, it isdischarged to the dust collector through the space defined between theouter upper surface of the separating chamber 303 and the bottom surfaceof the outer cover 314 of the outer chamber 302, and through the exhaustpipe 319. Thereafter, the more massive reclaimable particles and theparticle dust that do not get sucked out through the exhaust opening 307pass through the punched holes in the diffusion plate 311a and fall ontothe top of the diffusion plate 311b and then strike onto the top surfaceof the diffusion plate 311b to be dispersed. At this time, anyrelatively low mass particle dust that is present will be dispersedupwardly to pass through the punched holes in the diffusion plate 311a,and then it is sucked out of the exhaust opening 307. Then thereclaimable particles and the particle dust that have fallen onto thetop of the diffusion plate 311c through the punched holes of thediffusion plate 311b are further separated in the same manner as wasdescribed in connection with the diffusion plate 311b. This processcontinues until the reclaimable particles pass through the punched holesin the bottommost diffusion plate 311e, at which point the reclaimableparticles including a small amount of dust fall into the hopper 34. Atthis time, any relatively low mass particle dust that is still presentis sucked up through the second exhaust opening 308 and the spacedefined between the outer wall of the separating chamber 303 and theinner wall of the outer chamber 302, and then it is discharged to thewaste collector through the exhaust pipe 319. While this whole processis taking place, the relatively small bits of paint or coating aredischarged from the exhaust pipe 319. On the other hand, however, therelatively large bits of paint or coating that cannot pass through thepunched holes of the diffusion plates 311a-311e remain on the tops ofthe diffusion plates 311a-311e. To remove these large bits of paint, theouter cover 314 of the outer chamber 302 is opened after the blastingapparatus is turned off, and then the supporting rod 312 and thediffusion plates 311a-311e fixed thereto are removed from the outerchamber 302, thereby enabling to remove the large bits of paint easily.

Now, when the first pressured tank 1 runs out of particles, thedirectional control valve 20 is switched from the first pressured tank 1to the second pressured tank 11 by operating the changeover switch. Atthe same time, the operation of the changeover switch causes theparticle supply valve 17 and the air release valve 15 to close, and theair supply valve 13 to open to allow pressurized air to flow into thesecond pressured tank 11 in order to pressurize the inside of the secondpressured tank 11. By carrying out the above operation, a tank fromwhich particles are supplied to the nozzle 24 is changed from the firstpressured tank 1 to the second pressured tank 11 (see FIG. 4). This isindicated by "B Switching" in FIG. 5.

At the same time, the operation of the changeover switch to the secondpressured tank 11 causes the air supply valve 3 to close and the airrelease valve 5 to open in order to lower the pressure inside the firstpressured tank 1 to a level roughly equal to the atmospheric pressure.Next, by means of a timer (not shown in the drawings), the particlesupply valve 7 is opened to supply particles from the hopper 34 to theinside of the first pressured tank 1 a prescribed amount of time afterthe operations of the directional control valve 20, the air supply valve3 and the air release valve 5 have been carried out. In this connection,it should be understood that such delay of the operation of the particlesupply valve 7 by the timer assures that particles are supplied to thefirst pressured tank 1 from the hopper 34 only after the pressure insidethe first pressured tank 1 has reached a level roughly equal to theatmospheric pressure in order to prevent pressurized air from leakinginto the hopper 34.

Accordingly, by repeatedly carrying out the above described operation ofthe changeover switch, it becomes possible to continuously supplyparticles in either of the first pressured tank 1 or second pressuredtank 11 to the nozzle 24.

In this connection, it should be noted here that the present inventionis not limited to the provision of two pressured tanks as described inthe embodiment above. Instead, it is also possible to employ three ormore pressured tanks in the pressured tank apparatus according to thepresent invention. Furthermore, it is possible to employ an arrangementof two or more tanks having different capacities in the pressured tankapparatus according to the present invention. For example, in theembodiment described above, one of the pressured tanks 1, 11 may be alarge main tank while the other is a smaller subtank which is used onlyduring refilling operation of particles to the main tank.

As was stated previously above, the pressured tank apparatus accordingto the present invention, a tank from which particles are supplied to anozzle is selected from a plurality of pressured tanks, while theremaining tank or tanks which are not in use are being refilled withparticles, thus making it possible to carry out a continuous blastingoperation in which no suspension is required for refilling particles.

Further, as it is possible to utilize a plurality of small pressuredtanks in the pressured tank apparatus according to the presentinvention, a high degree of safety can be achieved and the overall sizeof the blasting apparatus can be kept to a minimum. As a result,manufacturing costs can be kept down and only a small amount of space isrequired to install the blasting apparatus.

Furthermore, when a predetermined amount of particles is supplied to theblasting chamber, it is detected by the level sensor. When suchdetection is made, the particles are fed to the particle separator whichparticles are being supplied to the other tank or tanks which is not inuse. Therefore, it is possible to save the time required to refillparticles to the tank, which makes it possible to carry out continuousblasting operation.

Moreover, since it is possible to use the reclaimable particles in theblasting chamber, it is not necessary to refill new particles from anupper portion of a pressured tank which is normally put at relatively ahigh position.

Next, with reference to FIG. 7 and FIG. 8, a detailed description of thepreferred embodiment of the particle supply valve 200 according to thepresent invention will now be given below.

FIG. 7 is a cross-sectional view of a particle supply valve 200according to the present invention, in which the valve 200 is shown inan open state. FIG. 8 is a cross-sectional view of the same valve 200shown in FIG. 7, in which the valve 200 is shown in a closed state.

As shown in FIGS. 7 and 8, the particle supply valve 200 has a valvehousing 201 made of brass. The valve housing 201 is provided with aninlet port 202 which allows particles and pressurized air to pass intothe valve, an outlet port 203 which allows particles and pressurized airto pass out of the valve, and a control air inlet/outlet port 204 whichallows control air to be supplied to and released from the valve.

Further, a brass partition wall 210 is integrally formed inside thevalve housing 201 to partition the space inside the valve housing into afirst chamber 215 and a second chamber 216. The inlet port 202 and theoutlet port 203 are communicated with the first chamber 215, and thecontrol air inlet outlet port 204 is communicated with the secondchamber 216.

Further a valve rod 207 which is also made of brass is slidably insertedthrough an insertion hole 211 formed in the central portion of thepartition wall 210. Provided on the tip end of the left side portion ofthe valve rod 207 which lies in the first chamber 215 is a hard rubbervalve element 206. The hard rubber valve element 206 is formed in theshape of a half sphere. By being tied to the valve rod 207, the valveelement 206 is movable to seal off an valve seat 205 of the inlet port202 in order to shut off the supply of particles and pressurized airflowing into the first chamber 215 of the particle supply valve 200. Toaccomplish this function, the valve element 206 is preferably formed tohave a diameter that is larger than the diameter of the valve seat 205.

Also, on the side of the valve rod 207 which lies in the first chamber215, there is provided a brass slide disc 209 which is fixed to thevalve rod 207. The slide disc 209 is formed such that the outercircumferential surface thereof is in sliding contact with the innercircumferential wall surface of the first chamber 215. As a result, theslide disc 209 makes it possible to divide the first chamber 215 into afirst space which receives particles and pressurized air and a secondspace which is kept free of particles and pressurized air.

Further, on the side of the valve rod 207 which lies in the secondchamber 216, there is provided a brass piston 208 which is fixed to thevalve rod 207. The outer circumferential surface of the piston 208 is insliding contact with the inner circumferential surface of the secondchamber 216. The circumferential surface of the piston 208 is widened tostabilize the sliding movement of the valve rod 207 and to provide ahighly effective airtight seal against the control air under pressure inthe second chamber 216. Further, a hard rubber shock absorber 217 isprovided in the second chamber 216 on the wall surface of the partitionwall 210.

Further, a biasing means 212 comprised of a metal spring is provided inthe second chamber 216 between a protruding portion formed with an endportion of the valve rod 207 which lies in the second chamber 216 andthe inner wall surface of the second chamber 216 which directly facesthe protruding portion of the valve rod 207. In particular, one end ofthe biasing means 212 is secured around the protruding portion of thevalve rod 207 and the other end of the biasing means 212 is securedinside an annular fixing member or spring retainer 213 provided on theinner wall surface of the second chamber 216. Further, a adjusting screw214 is inserted through the valve housing 201 in a manner that allows anend portion thereof to be screwed into the second chamber 216. Moreover,the adjusting screw 214 has a head portion lying outside the valvehousing 201 which can be turned to adjust the length of the end portionthereof protruding within the second chamber 215.

Now, when the supply of particles and compressed air to a nozzle 24(shown in FIG. 1) is to be shut off, as shown in FIG. 7, control air ispassed into the second chamber 216 through the control air inlet/outletport 204 to pressurize the second chamber 216, thereby causing thepiston 208 to be pushed toward the first chamber 215, and this in turncauses the valve rod 207 to slide to the left, whereby the valve element206 is formed into the valve seat 205 to seal off the inlet port 202.

On the other hand, when particles and compressed air are to be suppliedto the nozzle 24, the control air in the second chamber 216 is releasedthrough the inlet/outlet port 204 to depressurize the second chamber216, thereby causing the piston 208 to retract in a direction away fromthe first chamber 215, and this in turn causes the valve rod 207 toslide to the right, whereby the valve element 206 is pulled out of thevalve seat 205 (i.e., the valve element 206 moves to the right in FIG.8). As a result, particles and pressurized air first flow from the inletport 202 into the first chamber 215 through the space created betweenthe valve seat 205 and the valve element 206, and then flow out throughthe outlet port 203 to be supplied to the nozzle.

In this connection, because the slide disc 209 divides the first chamber215 into the first space which receives particles and the second spacewhich is kept free of particles , it is possible to prevent particlesfrom entering into the space between the insertion hole 211 and thevalve rod 207. As a result, it is possible to prevent the slidingsurfaces from being abraded by the particles.

Further, by turning the adjusting screw 214 to increase the protrudinglength of the end portion thereof inside the second chamber 216, it ispossible to reduce the distance between the left end of the adjustingscrew 214 and the right end of the valve rod 207, and this distancedefines the retraction distance of the valve element 206. Namely, asshown in FIG. 8, when particles and compressed air are being supplied tothe nozzle, the left end of the adjusting screw 214 is in contact withthe right end of the valve rod 207. Consequently, it is possible tocontrol the amount of particles and compressed air being supplied to thenozzle by turning the adjusting screw 214 to adjust the length of theend portion inside the second chamber 216.

Furthermore, because the valve housing 201, partition wall 210, valverod 207, piston 208 and slide disc 209 are made of brass, they have ahigher hardness than the particles. As a result, the valve is impartedwith excellent antiabrasion characteristics.

Moreover, because the wall surface of the partition wall 210 that liesinside the second chamber 216 is provided with the hard rubber shockabsorber 217, it is possible to prevent the piston 208 from collidingwith the partition wall 210, and this makes it possible to prevent thevalve element 206 from being damaged when the second chamber 216experiences a sudden rise in pressure.

In summary, because the particle supply valve according to the presentinvention does not use partition walls made of rubber, it is possible toavoid the deterioration in elasticity associated with such construction.As a result, the present invention provides a particle supply valvewhich prevents leakage of particles and compressed air.

Furthermore, because the partition wall, sliding wall and piston enablethe valve rod to maintain its sliding characteristics, it is possible toconsistently carry out a proper sliding operation with the valve rod. Asa result, the valve element fixed to the valve rod can consistently bemoved into a prescribed position in the opening, thus making it possibleto prevent particles and pressurized air from leaking through the valveseat.

Moreover, because the valve rod is held slidably by means of thepartition wall, the slide disc and the piston, it is possible to alwayscarry out precise sliding movement. Therefore, the valve element fixedto the valve rod can be brought into contact with the opening at aprescribed position, thereby preventing leaking of pressurized air andparticles.

Furthermore, in the event that the power source is erroneously shut offduring the blasting operation to terminate that control air flows intothe second chamber and pressurize it, the valve element is not retractedfrom the opening because the biasing means pushes the valve rod.Therefore, even in such a case, it is possible to prevent thepressurized air and particles from being ejected from the outlet port.

Moreover, since the slide disc inside the first chamber, it is possibleto prevent particles from entering into the sliding surfaces between theinsertion hole and the valve rod, thus making it possible to maintain anairtight seal between the first chamber and the second chamber over along period of time.

Moreover, the amount of particles to be supplied can be adjusted by theoperation of the adjusting screw.

Hereinafter, with reference to FIG. 10 and FIG. 11, a detaileddescription of a first embodiment of the particle separator 300according to the present invention will now be given below.

In this connection, FIG. 10 is a cross-sectional side view of a particleseparator according to the present invention, and FIG. 11 is a top planview thereof. As shown in these figures, the particle separator 300includes a cylindrically shaped outer chamber 302, a cylindricallyshaped separating chamber 303 arranged inside the outer chamber 302, anda hopper tank 304 arranged below the separating chamber 303 to collectreclaimable particles.

Provided in an upper portion of the circumferential wall of theseparating chamber 303 is an inlet port 306 which allows a mixture ofreclaimable particles and particle dust produced by a blasting operationto be fed together with pressurized air to the inside of the separatingchamber 303. As shown in FIG. 11, the inlet port 306 faces toward thecentral portion of the upper section of the separating chamber 303. Inthis connection, because the present invention does not utilize arotating flow of air, it is possible to provide a plurality of inletports 306. Further, the top of the separating chamber 303 is providedwith an inner cover 313 which has four first exhaust valve seats (ports)307 formed therein (see FIG. 11).

Inserted into the inside of the separating chamber 303 is a diffusionmember 310. The diffusion member 310 is supported by a stay 315 at alower portion thereof. The diffusion member 310 can be removed from theouter chamber 302 by opening the inner cover 313 and the outer cover314.

The diffusion member 310 includes five circular-shaped punched metaldiffusion plates 311a, 311b, 311c, 311d, 311e which are spaced aprescribed distance from each other and a diffusion plate support member12 which passes through a central portion of the respective diffusionplates 311a-311e to support the diffusion plates 311a-311e. FIG. 12 is aperspective view of the diffusion member 310. As shown in FIG. 12, thefive diffusion plates 311a-311e are spaced an equal distance from eachother in a layered arrangement that is fixed to the diffusion platesupport member 312.

In this connection, the diameter of each hole of the punched metaldiffusion plate is set in accordance with the diameter of thereclaimable particles. For example, based on experiments carried out bythe present inventor, it was determined that holes having a diameter of3 mm was preferred for reclaimable particles having a diameter of 0.8mm.

Further, four second exhaust valve seats (ports) 308 are formed in thetop of the hopper tank 304 and a particle discharge outlet 317 isprovided at the bottom of the hopper 304.

Further, a delivery pipe 305 passes through the outer chamber 302 fromthe left side of FIG. 10, whose blowing port 306 is opened in theseparating chamber 303. The delivery pipe 305 is connected to theblasting apparatus (not shown in the drawing) to deliver a mixture ofreclaimable particles and particle dust together with compressed air.Further, on the right side of the outer chamber 302, a dust dischargeport 318 is formed, to which an exhaust pipe 319 which sends particledust to a dust collector (not shown in the drawings) is connected.

Now, the operation sequence of the above-described particle separator300 will be given below. First, a mixture of reclaimable particles andparticle dust produced by a blasting operation is delivered to theinside of the separating chamber 303 together with compressed airthrough the delivery pipe 305. In this case, the dust collector (notshown in the drawings) is activated to create a negative pressure insidethe separating chamber 303. Therefore, the mixture of reclaimableparticles and particle dust which have entered the inside of theseparating chamber 303 from the inlet port 306 strike onto the innerwalls of the separating chamber 303, the bottom surface of the innercover 313 and the top surface of the uppermost diffusion plate 311a (theparticle reception surface) at high velocity and thereby being dispersedover the top surface of the diffusion plate 311a. At this time, becausethe particle dust has a smaller mass than the reclaimable particles, theparticle dust gets sucked out of the separating chamber 303 through thefirst exhaust openings 307 and passes through the upper space definedbetween the upper surface of the separating chamber 303 and the bottomsurface of the outer cover 313 of the outer chamber 302, and then theyare discharged from the dust exhaust port 318 to the dust collector viathe exhaust pipe 319.

At this point, the more massive reclaimable particles and the particledust that did not get sucked out through the first exhaust openings 307pass through the punched holes in the diffusion plate 11a and fall ontothe strike onto the top of the diffusion plate 311b to be dispersed. Atthis time, any relatively low mass particle dust that is present will besucked upwards again to pass through the punched holes in the diffusionplate 311a and out of the first exhaust openings 307. On the other hand,the reclaimable particles and particle dust that fall onto the diffusionplate 311c through the punched holes of the diffusion plate 311b areseparated again in the same manner described above.

This process continues until the reclaimable particles and the remainingparticle dust pass through the punched holes in the bottommost diffusionplate 311e, at which point they fall into the hopper tank 304. At thistime, any relatively low mass particle dust that is still present issucked up through the second exhaust openings 308 and the space definedbetween the outside walls of the separating chamber 303 and the insidewalls of the outer chamber 302, and then they are discharged through theexhaust port 318.

Now, as was described for the present embodiment, in addition to thefirst exhaust openings 307, the separating chamber 303 is provided withthe second exhaust openings 308 to allow the particle dust andcompressed air that have passed through the diffusion member 310 to besucked up and expelled out through the exhaust port 318. As a result,the particle separator 300 of this embodiment has an additional step forremoving particle dust. This prevents any particle dust from being mixedwith the reclaimable particle, which is advantageous to achieve a highlyaccurate separation.

Furthermore, in the present embodiment of the particle separatoraccording to the present intention, the first exhaust openings 307 arearranged so as to face with the top surface of the uppermost diffusionplate 311a of the diffusion member 310. As a result, it becomes possibleto easily suck out the particle dust diffused by the diffusion member310, thus enabling the present invention to achieve a high separationaccuracy.

Furthermore, in the present embodiment of the particle separatoraccording to the present invention, the first exhaust openings 307 arearranged above the top surface of the uppermost diffusion plate 311a ofthe diffusion member 310. As a result, it is possible to prevent thelarge-mass reclaimable particles from being sucked out through the firstexhaust openings 307, and this enables the present invention to achievean even higher separation accuracy.

Furthermore, in the present embodiment of the particle separatoraccording to the present invention, the second exhaust openings 308 areadditionally arranged in the top of the hopper tank 304. As a result, itis also possible to prevent the large-mass reclaimable particles frombeing sucked out through the second exhaust openings 308, and thisenables the present invention to achieve an even higher separationaccuracy.

Furthermore, in the present embodiment of the particle separatoraccording to the present invention, the diffusion member 310 can beeasily removed from the separating chamber 303 and the outer chamber 302by opening the inner cover 313 and the outer cover 314. As a result, itis possible to easily remove the relatively large bits of peeled paintthat remain on the tops of the respective diffusion plates 311a-311e.

Hereinafter, with reference to FIG. 13, a detailed description of asecond embodiment of a particle separator 300 according to the presentinvention will now be given below. In this regard, FIG. 13 is aperspective view of the second embodiment of the diffusion member 340 ofthe particle separator according to the present invention. In thisregard, the diffusion member 340 is interchangeable with theabove-described diffusion member 310 of the first embodiment of theparticle separator according to the present invention. Namely, incontrast with the diffusion member 310 of the first embodiment of theparticle separator which utilizes five punched metal diffusion plates311a-311e having a plurality of holes, the diffusion member 340 of thesecond embodiment of a particle separator utilizes an equally spacedlayered arrangement of five diffusion plates 341a-341e having aplurality of slits formed therein. In this embodiment, as shown in FIG.13, each slit plate is rotatably supported by a diffusion plate supportmember 342.

Now, in the arrangement shown in FIG. 13, the slits of adjacentdiffusion plates are out of alignment with each other. Such anarrangement facilitates diffusion of the mixture of reclaimableparticles and particle dust, which leads to increased amount of wastematerial sucked out through the first exhaust openings 307. However, iftoo much diffusion is created, some of the reclaimable particles may bemixed into the waste material and such reclaimable particles get suckedout together with the waste material to be expelled through the firstexhaust openings 307. For this reason, it may be necessary to lower thedegree of diffusion created by the diffusion member 340.

In this connection, it is possible to adjust the degree of diffusioncreated by the diffusion member 340 by rotating one or more of thediffusion plates 341a-341e to change the direction of the slits thereofwith respect to the slits of adjacent diffusion plates. For example, itis possible to rotate the three diffusion plates 341a-341c in order toalign the slits of the diffusion plates 341a-341c with each other. Ifthis is done, the mixture of reclaimable particles and particle dustwill easily pass through the slits of the first three diffusion plates341a-341c and then become widely diffused at the diffusion plates 341dand 341e which are located relatively far from the first exhaustopenings 307. As a result, it is possible to prevent the reclaimableparticles from being sucked out through the first exhaust openings 307.

Thus, by simply rotating one or more of the diffusion plates 341a-341e,a user of the particle separator can adjust the degree of diffusioncreated by the diffusion member 340 in order to prevent reclaimableparticles from being expelled to the dust collector.

In summary, according to the second embodiment as described above, itbecomes possible to prevent the reclaimable particles from beingexpelled to the dust collector by adjusting the diffusion efficiency byrotating each diffusion plate appropriately.

INDUSTRIAL UTILIZATION

As described above, a blasting apparatus according to the presentinvention is particularly useful, as is known, in peeling operation ofpaint or surface processing which are applied onto the surface ofmetals, resin materials or woods, and it is particularly suitable in acontinuous blasting operation. Further, the blasting apparatus accordingto the present invention can be realized in any blasting apparatuseswhich include a relatively small blasting apparatus in which operationis carried out under the condition that an operator holds a nozzledirectly through a protection material and a relatively large blastingapparatus which are used in outer surface processing of trains or thelike.

What is claimed is:
 1. A particle supply valve for use in a blasting apparatus, wherein said valve supplies abrasive particles to the blasting apparatus by means of applying pressurized air, comprising:a valve housing having a space inside thereof; a partition wall dividing the space of said valve housing into a first and second chamber each having inside walls; a particle inlet and a particle outlet both provided in said first chamber; a control air inlet/outlet port provided in said second chamber; a valve rod having two ends which is slidable and penetrates said partition wall to extend within each of the first chamber and the second chamber; a valve seat formed at the particle inlet; a valve element provided at one of the ends of the valve rod so as to open or close the valve seat by the sliding of said valve rod; a slide disc provided along a portion of the valve rod positioned within the first chamber so as to contact and slide freely along the inside wall of said first chamber; a piston fixedly mounted to the valve rod positioned within the second chamber for pressing said valve rod against the valve seat when pressurized air is applied through the control air inlet/outlet port; a shock absorber provided at a peripheral region of the partition wall positioned in the second chamber; an adjusting screw positioned within and through the inside wall of the second chamber which is opposite to the partition wall and shock absorber, which screw contacts the other end of the valve rod and determines maximum valve clearance of the valve seat; and a biasing means arranged around the valve rod positioned between the piston and the inside wall of the second chamber through which the screw is positioned.
 2. The valve of claim 1, wherein the shock absorber is made from hard rubber materials.
 3. The valve of claim 1, wherein the biasing means is a spring. 